1. Field of Invention
The invention pertains to a fixing device and, in particular, to a fixing device that fixes a printed circuit board (PCB) onto a shell to provide the functions of vibration reduction and circuit grounding.
2. Related Art
With the tremendous advance in technologies, computers are widely used in all kinds of businesses. Therefore, high-level server uses become more popular. To ensure the stability and reliability of the high-level servers, the problems of electromagnetic interference (EMI) or electromagnetic compatibility (EMC) have received a lot of attention in recent years.
To solve the above-mentioned problems and to achieve the effect of fixing a PCB to a shell, a conventional means is proposed, as shown in FIGS. 1 and 2. Take a common PCB 8 (computer mother board) as an example. A conductive fixing pillar 9 fixed on a shell 100 penetrates through a ground pad (the through hole 80) on the PCB 8. An adjacent clamping hole 81 then holds the neck 90 of the pillar 9, achieving the goals of both fixing and electric conduction.
FIGS. 3 and 4 show another conventional method. First, the elastic washer 104 goes through a ground pad 103 on a PCB 102 and snaps the PCB 102 through a groove. A fixing pillar 105 is then inserted through the same ground pad 103 and pushed to the side, so that the neck of the fixing pillar 105 is held onto the ground pad 103. Finally, the tail of a mask 101 is hooked with the tail of the ground pad 103. An opening above it is provided for the elastic washer 104 to hole the mask 101 and the fixing pillar 105, thereby fixing the PCB 102 onto the shell 100.
However, good EM wave shielding effect and lower costs are hard to simultaneously achieve. Although the example shown in FIGS. 1 and 2 is cheap in its cost, there may be sliding when external vibrations occur. The elastic washer in FIGS. 3 and 4 has a larger contact area with the PCB, providing a better grounding and mask fixing; however, the structure and thus the assembly procedure are complicated. Moreover, one has to reserve extra space when designing the PCB, making the cost increase inevitable.